Ratings by movie reviewers are ubiquitous, from thumbs up or down to a star-rating system or any kind of sliding point system. Are they a waste of time that should be avoided and abolished, a necessary marketing tool to pull readers in to read reviews, or an objective measurement of the reviewer’s overall evaluation of a movie?

During my days as Managing Partner at Box Office Mojo, when the site still published movie reviews, we struggled with this question. Initially we used a letter grade scoring system.

However, the grading system was a source of consternation for us and our reviewers. Readers of the site would often write in and say, “How could you give such-and-such movie a C+ and then give thus-and-so movie an A-?!” Some of them clearly had not even read the reviews and were writing solely on the basis of the grades—and in some instances readers hadn’t bothered to notice the two reviews were written by different people. Sadly, such trifle led us to decide to do away with the rating system.

(In July of 2008, we sold the company to Amazon.com, an acquisition for IMDb.com, which Amazon owns. Post-sale, they decided to stop producing reviews which, incidentally, was probably the right move for the company as they were a money-losing proposition and generally disliked by the site’s readers).

I’m not sure axing the rating system was the right choice. The need for succinct headlines was still there to draw attention, and we found ourselves changing our headline policy to be more evaluative in order to draw readers in. We had avoided a specific rating system per se, but succumbed to the purpose a rating system is meant to employ.

That purpose is to draw attention. Whether for a movie review or a headline to a news article, there is an objective need to draw the readers’ attention and state why an article or review is important.

Arguably, a rating scale achieves that purpose in the quickest way possible. It is a succinct, immediate advertisement of the reviewer’s evaluation of the movie. It can also help the movie-goer who doesn’t like to read reviews prior to seeing a movie be given an indication of the review without having to read or know anything about the movie prior to seeing it.

However, a rating is not a substitute for a review, so those who try to compare one movie’s rating to another’s are dropping the context of the overall purpose here. How could I give, for example, the movie Liar Liar an A while giving an A- to We Were Soldiers? Both are very different movies and in some ways I like We Were Soldiers better (click here to read my review of Were Were Soldiers).

But a rating is not meant to be used as a comparison tool to rank different movies and that is not its purpose. The rating pertains to the movie in question, and should indicate whether the movie was interesting, entertaining and/or fulfilling on its own terms. It is a teaser or overall summary of the reviewer’s evaluation and only that. A reviewer should expound the reasons for liking or disliking a movie in his review.

(As an aside, reviewers should only assign a rating after they’ve written their review, and make sure their rating matches what they actually say about the movie. Otherwise the reviewer could find himself trying to justify his initial rating rather than focus on what he has to communicate about the movie.)

So what is the best rating scale to use? While there are no hard and fast rules, I believe a scale of one to four to be ideal—whether stars or letter grades or some other method is used is not important. The lowest rating should be reserved for an “I hated it” or “very bad” evaluation; the second for a “mixed” review, and then two scales of positive: “liked it” or “pretty good” and “loved it” or “excellent.”

Just as the concept “big” gives an indication of something’s size, but is no substitute for its more precise measurement, so a movie rating give an indication of a reviewer’s evaluation of movie but is no substitute for reading the actual review.